What are the diagnostic criteria and treatment options for a Crohn's disease flare?

Diagnosis of Crohn's Disease Flare

Diagnosis of a Crohn's disease flare requires a combination of clinical assessment, laboratory biomarkers, and imaging studies, with fecal calprotectin >150 mg/g being the most reliable non-invasive marker to confirm active inflammation. 1

Initial Diagnostic Evaluation

Laboratory Tests

• Essential laboratory tests: 1, 2

  • Full blood count (including hemoglobin, leukocyte count, platelet count)
  • C-reactive protein (CRP) - elevated in active inflammation
  • Erythrocyte sedimentation rate (ESR)
  • Serum electrolytes
  • Liver function tests
  • Serum albumin (to assess nutritional status and degree of inflammation)
  • Renal function

• Stool tests: 1

  • Fecal calprotectin - most sensitive and specific non-invasive marker for intestinal inflammation

    • 150 mg/g indicates active inflammation

    • Values >250 mg/g suggest severe disease
  • Stool cultures to exclude infectious causes
  • Clostridium difficile toxin assay - mandatory before escalating therapy
  • Consider testing for Cytomegalovirus (CMV) in moderate to severe colitis

Biomarker Interpretation

• Fecal calprotectin: 1, 2

  • <50 mg/g: Normal
  • 50-150 mg/g: Mild disease
  • 150-250 mg/g: Moderate disease

  • 250 mg/g: Severe disease

• CRP and ESR interpretation: 2

  • Both elevated: Active inflammation (both acute and chronic processes)
  • CRP elevated, normal ESR: Acute inflammation (early flare)
  • Normal CRP, elevated ESR: Chronic inflammation or non-inflammatory factors

Imaging Studies

First-line Imaging

• Cross-sectional imaging is recommended to detect strictures and extra-luminal complications 1

• MR enterography (MRE) is preferred over CT for monitoring Crohn's disease to limit radiation exposure 1

  • Excellent for detecting transmural inflammation and extraluminal complications
  • Similar diagnostic accuracy to CT but without radiation exposure
  • Signs of disease activity: increased bowel wall thickness, vascularity, contrast enhancement, reduced bowel motility

• Contrast-enhanced CT is the key study in emergency settings to assess: 1

  • Abscesses
  • Fistulae
  • Source of bleeding in gastrointestinal hemorrhage

• Intestinal ultrasound (IUS) can be useful when CT is not available 1

  • Can show free fluid, abscesses, or intestinal distention
  • High sensitivity for small bowel disease (92%)

Endoscopic Evaluation

• Ileocolonoscopy with biopsies is the gold standard for assessing disease activity 1

  • In acute severe colitis, flexible sigmoidoscopy is usually sufficient 1
  • Typical endoscopic findings: 3
    • Non-continuous distribution of longitudinal ulcers
    • Cobblestone mucosal appearance
    • Aphthous ulcerations arranged in a longitudinal fashion

• Histological assessment: 3

  • Focal and patchy chronic inflammation
  • Focal crypt irregularity
  • Non-caseating granulomas

Diagnostic Algorithm for Crohn's Disease Flare

1. For patients with moderate to severe symptoms: 1

   • If fecal calprotectin >150 mg/g, elevated CRP, or elevated fecal lactoferrin → Active inflammation is confirmed
   • Proceed with treatment adjustment without mandatory endoscopic assessment

2. For patients with mild symptoms: 1

   • If elevated inflammatory markers (fecal calprotectin >150 mg/g, elevated CRP) → Endoscopic assessment recommended before treatment adjustment

3. For suspected complications: 1

   • Perform cross-sectional imaging (MRE or CT) to assess for strictures, fistulae, or abscesses

Common Pitfalls to Avoid

1. Failing to rule out infectious causes before escalating immunosuppressive therapy 1, 2

   • Always test for C. difficile and consider CMV in moderate to severe colitis

2. Relying solely on symptoms for disease assessment 1

   • Symptoms may not correlate with objective measures of inflammation
   • Combine symptoms with biomarkers for more accurate assessment

3. Overuse of CT scans in young patients 1

   • MRE is preferred for routine monitoring to reduce radiation exposure

4. Assuming normal CRP rules out active disease 1, 2

   • CRP has low sensitivity in some patients with active disease
   • Fecal calprotectin is more reliable for detecting intestinal inflammation

5. Misdiagnosing other conditions as Crohn's flare 4

   • Consider intestinal tuberculosis, Behçet's disease, and other mimics in differential diagnosis

By following this systematic approach to diagnosis, clinicians can accurately identify Crohn's disease flares and distinguish them from other conditions, leading to appropriate and timely treatment decisions.